1. Field of the Invention
This invention is in the field of chart recorders having a movable print head.
2. Description of the Prior Art
There have been proposed various fixed and moveable print head devices for producing graphs. Such chart recorders employ ink, heat, electrostatics and mechanical means for marking one or more graphs on a moving chart medium. Various of these recorders have introduced the concept of marking both the analog graph representations and alphanumeric symbols on the chart paper for various purposes.
For example, U.S. Pat. No. 3,754,279 to Valenti shows the use of a separate print head for recording data points on a chart, while a graph is recorded using a separate stylus. It is also possible to record digital information together with analog graph markings with a fixed print head, such as the thermal or electrostatic type. U.S. Pat. No. 3,394,383 to Lloyd and U.S. Pat. No. 3,815,144 to Aiken show chart recorder devices utilizing fixed rows of dots capable of providing alphanumeric information with the appropriate input. U.S. Pat. No. 3,840,878 to Houston shows a recorder which operates in one of two modes to record a graph and character on graph paper. The printing mechanism consists of individually energizable thermal printing elements in a thermal element matrix. While the Houston apparatus shows the marking of graphs with an identifying alphanumeric symbol, there is no indication in Houston of offset printing means for either multiple digit graph numbering or other special purpose offset alphanumeric symboling.